The present invention generally relates to molding compositions, particularly moldable inorganic compositions, and to making ceramic microstructures such as plasma display panel barrier ribs using inorganic molding compositions.
Plasma display panels (PDP) include a pair of glass flat panels arranged parallel to each other and spaced a distance apart via barrier ribs. The barrier ribs are also arranged to form partitions between the glass panels that can contain an inert gas (e.g., neon, helium, xenon). The partitions are used in part to form a grid of discharge cells corresponding to pixels or sub-pixels in the plasma display that can be individually activated when an electric field is applied across a cell. The electric field excites the inert gas, which gives off ultraviolet radiation that irradiates a phosphor material contained within the cell to in turn give off visible light.
Commonly, PDP barrier ribs are formed using a composition containing an inorganic component, such as glass or ceramic material, and an organic component, such as a curable organic binder. Such compositions can be used to make barrier ribs by employing various techniques including mask-based techniques such as photolithography or sandblasting, screen printing techniques, and direct molding techniques.
When making barrier ribs using compositions that contain glass or ceramic material in an organic binder, it may be desirable to initially form the ribs by curing or otherwise hardening the organic material and then to remove the organic binder component from the ribs by sintering. In the case of many barrier rib compositions, the organic binder component contained therein is capable of forming a polymer compound as a result of curing or hardening. The organic binder component can then subsequently be removed from the ribs by thermal decomposition during sintering. To remove the organic components, sintering can be carried out at relatively high temperatures (e.g., 550xc2x0 C. to 650xc2x0 C.) for relatively long period of time (e.g. 30 minutes to 1 or more hours). In general, the higher the sintering temperature, the more likely it is for the panel substrate to warp, shrink, or otherwise distort during processing.
In some PDP rib fabrication processes, it may also be desirable to remove one or more organic additives other than the binder component that may be contained in the rib composition prior to the sintering step that bums out the binder. Additional removal steps generally require additional heating cycles for additional amounts of time, and each heating cycle generally requires temperature control. This can greatly reduce the efficiency of the rib fabrication process.
According the present invention, there can be provided a molding composition suitable for making ceramic microstructures (such as PDP barrier ribs) at comparatively low sintering temperatures. Using a molding composition of the present invention in a process of making ceramic microstructures on a glass panel substrate can reduce the likelihood of warpage, distortion, shrinkage, or other types of deformation of the glass substrate. The use of a molding composition according to the present invention can also increase the efficiency of a ceramic microstructure fabrication process by reducing the number of heating cycles, especially when multiple organic components can be removed at the same relatively low temperature.
It is another object of the present invention to provide a substrate for plasma display panels using a molding composition in accordance with the present invention to mold barrier ribs onto glass substrates.
It is still another object of the present invention to provide a method of producing barrier ribs on a glass substrate for plasma display panels.
In one embodiment, the present invention provides a molding composition that includes a glass or ceramic powder; an organic binder component capable of being hardened by exposure to heat, light, or an electron beam; and a debinding catalyst of the organic binder component, the debinding catalyst being a transition metal oxide, salt, or complex. The molding composition has a sintering temperature that is at most about 500xc2x0 C., and the presence of the debinding catalyst in the molding composition enables the use of lower sintering temperature ceramic formulations.
In another embodiment, the present invention provides a plasma display panel. The plasma display panel includes a glass panel having a plurality of barrier ribs formed thereon. The barrier ribs are formed using a molding composition that contains an inorganic component including a glass or ceramic powder, an organic binder component capable of being hardened by exposure to heat, light, or an electron beam, and a debinding catalyst of the organic binder component, the debinding catalyst comprising a transition metal oxide, salt, or complex, wherein the molding composition has a sintering temperature that is at most about 500xc2x0 C., and wherein the presence of the debinding catalyst in the molding composition enables the use of lower sintering temperature ceramic formulations.
In another embodiment, the present invention provides a method of making barrier ribs for a plasma display panel, which includes the steps of placing a molding composition between a mold having a plurality of concave portions and a glass panel, hardening the molding composition between the mold and the glass panel to form precursor barrier ribs, removing the mold from the precursor barrier ribs, and sintering the precursor barrier ribs on the glass panel by heating to a temperature of about 400xc2x0 C. to 500xc2x0 C. The molding composition contains an inorganic component including a glass or ceramic powder, an organic binder component capable of being hardened by exposure to heat, light, or an electron beam, and a debinding catalyst of the organic binder component, the debinding catalyst comprising a transition metal oxide, salt, or complex, wherein the molding composition has a sintering temperature that is at most about 500xc2x0 C., and wherein the presence of the debinding catalyst in the molding composition enables the use of lower sintering temperature ceramic formulations.